Mechanical log

[davelef]

I have recently purchased an old 25ft yacht which has no electronic log. Although I have a handheld gps which will tell me SOG I need to know speed through water to accurately plot course on paper bearing in mind I am in the Channel Islands so cant just discount up to 6kt of tide on springs(unless someone can tell me a way to do this in reverse from gps?) I was therefore thinking of purchasing a mechanical trailing log but have had difficulty tracking one down (other than antiques from 19th century for £500!) Can anyone suggest where I might get hold of one (new or used)or any other alternative way of calculating speed & distance? Thanks in advance for any help.

 

[Searush]

Am I just dense or are you trying to reverse engineer your plot? As I understand it the point of agregating course & speed thro' water with the tide set and drift is to calculate your C&SOG on the chart.

COG & SOG are read direct from GPS so why do you need to work backwards - unless GPS fails, of course. By all means draw it on the chart if it makes you feel better, but plotter GPS's will record your track anyway won't they?

Watch e-bay & boaty selling sites (see my sig below) or visit as many boat jumbles as you can for used stuff if you really feel you must know your water speed.

 

[VicS]

One of thse perhaps:

 

[davelef]

No you're not being dense - and neither am I, I don't think. Surely GPS gives me COG but not course to steer which is what I need to have speed through water for in order to calculate - otherwise I am surely just fighting the tide the whole time?

 

[davelef]

Yes - but where do I get hold of one and how much is it likely to set me back?

 

[VicS]

[ QUOTE ]
Yes - but where do I get hold of one and how much is it likely to set me back?

[/ QUOTE ] As others have suggested boat jumbles, ebay, anywhere selling second hand boat stuff. The "for sale board" on these forums and others (Have you put an ad' on the "wanted "board ?)

Going to cost a few 10s of £s I guess depending on condition but they dont attract ridiculous prices as they are not that popular now. If one is advertised as complete it should have spare line, spare sinker, spare crimps, spare glass and oil and instructions. You will also want the pair (one for stbd and one for port side) of mounting shoes. Everything you can see in the picture in fact. They did later do an economy version that came without all the spares and the wooden box. (My one was new in 1979 and cost £86.82 on 9 June from The Yachtmail Company Ltd in W11)

 

[Seagreen]

Keep your eye out on Ebay and other online auction sites - all good fun and you occasionally get a bargain.

 

[Seagreen]

Wow, VicS - that looks like a nice one.

 

[KenMcCulloch]

[ QUOTE ]
Wow, VicS - that looks like a nice one.

[/ QUOTE ] Doesn't it just. I have a similar one on Border maid that I bought on ebay in May for about £100. (I felt that a 60 y.o. wooden boat was naked without a Walker Log.) They come up regularly and the going rate seems to be about 100 notes or so. The ones in styrofoam packages without all the nice bits and pieces and the wooden box command slightly lower prices.

 

[alec]

I think logs can be fun but were never that reliable. Weed /heeling/losing etc made them a pain. But at the time there was not much else.

For me, GPS does it all.

If I want to know what the tide is doing I look at the diamonds on the chart, tidal stream atlas, or ( best) Reeve -fowkes books. I then make a calculation using the GPS data. If you are making a longish voyage you have to use this kind of data to plan the trip anyway.

The other fun thing to do at anchor is time/distance using things floating by on the water.

I get the feeling that you are thinking of logs as a must. Bit confused.

 

[davelef]

Now I think I am confused! When you say [ QUOTE ]
I then make a calculation using the GPS data.

[/ QUOTE ] what calculation and what data do you mean?

 

[roly_voya]

They are hard to get as no longer made and very useful for backup in case of electrical failure. The walker is considered the rolls royce but only shows distance not speed. The wasp is a bit more modern and shws speed on a car type clock with digital milometer. While these are very good I would be hesitant to use one all the time arounf the C/I due to the risk of snagging an impellor (impossible to replace). Fitting an impellor log is not difficult, any reason for not doing this?

For plotting the gps is fine, thats the line you put on the chart but you can't work an accurate speed through the water from it as you would need to know exactly the rate and set of the tide which is only ever an approximation which does leave you short on planning info

 

[homa]

I used to have a Stowe trailing log - all electric apart from the fish at the end of the wire. Was very accurate - gave distance and speed. No holes to drill in hull, just a couple of screw holes to mount the display. If I remember correctly it ran on 12v ship's power and could run on its own internal batteries if required. Might be worth a google to find a secondhand one - you might be lucky

 

[cliffordpope]

Put knots at measured intervals in a long length of rope, tie a log on the end, and throw it over the stern. Count the rate at which the knots pass over the taffrail.

 

[Evadne]

I've still got a Stowe trailing log, though it's showing its age. I see there is one for sale in boats and outboards.

 

[awol]

Perhaps I'm being dense too, but if you know the ground track you want to follow why not just sail to that using COG on the GPS and ignore the magnetic compass? .... and carry a spare GPS!

 

[StanFolds]

Here's one on ebay. http://cgi.ebay.co.uk/Walkers-Knotmaster...1QQcmdZViewItem
Stan

 

[VicS]

Not quite complete , most importantly no mounting shoes. Not much good without them and not now available, afaik. Someone bit a bit of sheet brass and some basic metal working skills would be able to make something though.

 

[Phoenix of Hamble]

Shoes now available via eBay

 

[davelef]

By following COG it is surely far more inefficient as it ignores the tide (which as mentioned before can be up to 6kts around here on a big spring). One of the primary reasons of plotting a course especially over a longer journey where the tide may turn in the opposite direction is surely to maximise use of the tide - which just sticking to COG certainly doesnt - or maybe I'm just old fashioned!!